External fixator assembly

ABSTRACT

External fixator assemblies, systems, and methods thereof. An external fixator system may include a plurality of fixator assemblies configured to connect a plurality of pins, for example, positioned on opposite sides of a fractured bone, with one more rods. The fixator assemblies may include a plurality of clamp assemblies positioned along a shaft and which are configured to rotate relative to one another when the fixator assembly is in an unlocked position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation application of U.S. patentapplication Ser. No. 14/957,793, filed on Sep. 15, 2017 (published asU.S. Patent Publication No. 2017-0156758), which is herein incorporatedby reference in its entirety.

BACKGROUND Field of the Invention

The present invention relates to external fixator assemblies, and, inparticular, to external fixator assemblies having a plurality of clamps.

Description of the Related Art

External fixators have long been used in trauma incidents as a long-termcare solution for reducing fractures and promoting bone healing.Recently, however, external fixators have been used for poly-traumaticpatients as a way to stabilize fractures until a more definitive methodof fixation can be determined and applied. The use of current externalfixators to perform this temporary stabilization can be bulky andtime-consuming.

Accordingly, there exists a need for lightweight, quick-assemblyexternal fixators.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

According to one embodiment, an external fixator system may include aplurality of external fixator assemblies configured to connect aplurality of pins, for example, positioned on opposite sides of afractured bone, with one more rods. The fixator assemblies may include aplurality of clamp assemblies which are configured to rotate relative toone another when the fixator assembly is in an unlocked position. Oncethe relative positioning of the pins and/or rods is achieved, forexample, to stabilize the bone or bones, the fixator assemblies may bemoved to a locked position, such that the clamp assemblies are fixed inposition and no longer able to rotate relative to one another.

In one embodiment, the external fixator assembly includes a shaft havinga distal end and a proximal end. The proximal end has at least oneexternal thread. A plurality of clamp assemblies extends along the shaftfrom the distal end to the proximal end. A biasing member is disposedbetween adjacent of the plurality of clamp assemblies. A cap assembly isdisposed over the proximal end of the shaft. The cap assembly is adaptedto bias the plurality of clamp assemblies toward the distal end of theshaft.

In an alternative embodiment, the external fixator assembly includes ashaft comprising a distal end having a flange and a proximal end havingat least one external thread. A clamp assembly is disposed along theshaft, proximal of the distal flange. A ratchet assembly biases theclamp assembly toward the distal flange. The ratchet assembly comprisesa ratcheting buttress having a radially extending buttress flange and ahole extending through the flange. The hole is sized to allow the shaftto extend therethrough. A plurality of fingers extends proximally aroundthe hole. Each of the plurality fingers has a plurality of internalratchet teeth adapted to engage the least one external thread on theproximal end on the shaft. A ratchet housing has a distal end having aradially extending housing flange adapted to engage the buttress flangeand a proximal end having at least one internal thread adapted tothreadably engage the at least one external thread on the shaft.

In still another alternative embodiment, the external fixator assemblyincludes a ratchet assembly. The ratchet assembly comprises a ratchetingbuttress and a ratchet housing. The ratcheting flange having an annularflange having a buttress axial hole formed therein, a tang extendingoutwardly from the annular flange in a first direction, and a pluralityof fingers extending outwardly from the annular flange in the firstdirection. The plurality of fingers surrounds the hole. Each of theplurality fingers includes a plurality of internal ratchet teeth. Theratchet housing has an annular flange having a housing axial hole formedtherein and a body attached to the flange. The annular flange has anexternal contoured surface, a first radially extending cavity adapted toreceive the annular flange of the wrenching buttress, and an axiallyextending slot adapted to receive the tang. The body has a plurality ofexternal flat surfaces extending around an outer perimeter thereof, asecond radially extending cavity adapted to receive the plurality offingers, and an internally threaded passage adjacent to the secondradially extending cavity.

In yet another alternative embodiment, the external fixator assemblycomprises a first shaft having a first coupling end and a first freeend, a second shaft having a second coupling end and a second free end,and a coupling pivotally retaining the first coupling end and the secondcoupling end. A first clamp assembly is disposed on the first shaftbetween the coupling and the first free end. The first clamp assemblycomprises a first inner clamp member disposed proximate to the coupling.The first inner clamp member has a first inner slot. A first outer clampmember is disposed proximate to the first free end. The first outerclamp member has a first outer slot. A first biasing member is disposedin the first inner slot and the first outer slot such that first biasingmember biases the first inner clamp member toward the first outer clampmember. A second clamp assembly is disposed on the second shaft betweenthe coupling and the second free end. The second clamp assemblycomprises a second inner clamp member disposed proximate to thecoupling. The second in the clamp member has a second inner slot. Asecond outer clamp is disposed proximate to the second free end. Thesecond outer clamp member has a second outer slot. A second biasingmember is disposed in the second inner slot and the second outer slotsuch that the second biasing member biases the second inner clamp membertoward the second outer clamp member.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and advantages of the present invention willbecome more fully apparent from the following detailed description, theappended claims, and the accompanying drawings in which like referencenumerals identify similar or identical elements.

FIG. 1 is a perspective view of an external fixator assembly accordingto a first exemplary embodiment being used to fixate adjacent bones;

FIG. 1A is a perspective view of the external fixator assembly shown inFIG. 1 being used to fixate broken pieces of the same bone;

FIG. 2 is a perspective view of the external fixator assembly shown inFIG. 1 with a rod and a pin connected thereto;

FIG. 3 is an exploded perspective view of the external fixator assemblyshown in FIG. 1;

FIG. 4 is a side elevational view, in section, of the external fixatorassembly shown in FIG. 1;

FIG. 5 is an exploded sectional view of a ratchet assembly used with theexternal fixator assembly shown in FIG. 1;

FIG. 6 is a perspective view of external fixator assembly according to asecond exemplary embodiment being used to fixate adjacent bones;

FIG. 7 is a perspective view of the external fixator assembly shown inFIG. 6 with rods connected thereto;

FIG. 7A is a perspective view of the external fixator assembly shown inFIG. 6 with a rod and a pin connected thereto;

FIG. 8 is an exploded perspective view of the external fixator assemblyshown in FIG. 6;

FIG. 9 is a side elevational view, in section, of the external fixatorassembly shown in FIG. 6; and

FIG. 10 is a side elevational view, in section, of the external fixatorassembly shown in FIG. 9, with one shaft pivoted relative to the othershaft.

DETAILED DESCRIPTION

In the drawings, like numerals indicate like elements throughout.Certain terminology is used herein for convenience only and is not to betaken as a limitation on the present invention. The terminology includesthe words specifically mentioned, derivatives thereof and words ofsimilar import. The embodiments illustrated below are not intended to beexhaustive or to limit the invention to the precise form disclosed.These embodiments are chosen and described to best explain the principleof the invention and its application and practical use and to enableothers skilled in the art to best utilize the invention.

Reference herein to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment can be included in at least one embodiment of theinvention. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment, nor are separate or alternative embodiments necessarilymutually exclusive of other embodiments. The same applies to the term“implementation.”

As used in this application, the word “exemplary” is used herein to meanserving as an example, instance, or illustration. Any aspect or designdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe word exemplary is intended to present concepts in a concretefashion.

Additionally, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or”. That is, unless specified otherwise, or clearfrom context, “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, if X employs A; X employs B; or Xemploys both A and B, then “X employs A or B” is satisfied under any ofthe foregoing instances. In addition, the articles “a” and “an” as usedin this application and the appended claims should generally beconstrued to mean “one or more” unless specified otherwise or clear fromcontext to be directed to a singular form.

Unless explicitly stated otherwise, each numerical value and rangeshould be interpreted as being approximate as if the word “about” or“approximately” preceded the value of the value or range.

The use of figure numbers and/or figure reference labels in the claimsis intended to identify one or more possible embodiments of the claimedsubject matter in order to facilitate the interpretation of the claims.Such use is not to be construed as necessarily limiting the scope ofthose claims to the embodiments shown in the corresponding figures.

It should be understood that the steps of the exemplary methods setforth herein are not necessarily required to be performed in the orderdescribed, and the order of the steps of such methods should beunderstood to be merely exemplary. Likewise, additional steps may beincluded in such methods, and certain steps may be omitted or combined,in methods consistent with various embodiments of the present invention.

Although the elements in the following method claims, if any, arerecited in a particular sequence with corresponding labeling, unless theclaim recitations otherwise imply a particular sequence for implementingsome or all of those elements, those elements are not necessarilyintended to be limited to being implemented in that particular sequence.

Also for purposes of this description, the terms “couple,” “coupling,”“coupled,” “connect,” “connecting,” or “connected” refer to any mannerknown in the art or later developed of joining or connecting two or moreelements directly or indirectly to one another, and the interposition ofone or more additional elements is contemplated, although not required.Conversely, the terms “directly coupled,” “directly connected,” etc.,imply the absence of such additional elements.

The present disclosure provides embodiments of external fixators thatcan be used to secure bone fractures. The inventive external fixatorsprovide connections that enable a surgeon to rapidly and securelystabilize the fracture.

According to one embodiment, an external fixator system may include aplurality of external fixator assemblies configured to connect aplurality of pins, for example, positioned on opposite sides of afractured bone, with one more rods. Each fixator assembly may include aplurality of clamp assemblies which are configured to rotate relative toone another when the fixator assembly is in an unlocked position. Oncethe relative positioning of the pins and/or rods is achieved, forexample, to stabilize the fractured bone or bones, the fixatorassemblies may be moved to a locked position, such that the clampassemblies are fixed in position, thereby stabilizing the fracture.

Referring to FIGS. 1-5, an external fixator assembly 100 (“fixatorassembly 100”) according to a first exemplary embodiment is shown. Asshown specifically in FIGS. 1 and 1A, fixator assembly 100 is used inconjunction with rods 50 and pins 60 to secure and stabilize adjacentbones 70, 72 (shown in FIG. 1) or to stabilize broken pieces 74, 76 ofthe same bone 70 (shown in FIG. 1A). While a femur 70 and a tibia 72 areshown in FIG. 1, and femur 70 is shown in FIG. 1A, those skilled in theart will recognize that fixator assembly 100, along with rods 50 andpins 60, can be used to fixate other bones, and other bone pairs aswell. Examples of bones may include, but are not limited to, the femur,tibia, fibula, humerus, radius, ulna, and phalanges. Although specificconfigurations of the external fixator systems are exemplified herein,it will be appreciated that the number, type, and location of rods 50,pins 60, and fixator assemblies 100 can be modified or changed based onthe type and location of the bone, fracture, surgeon preference, and thelike.

As shown in FIG. 2, fixator assembly 100 can be used to releasablysecure rod 50 and pin 60 through the use of a plurality of connectorassemblies. In an exemplary embodiment, rod 50 can be constructed from arigid material, such as, for example, a carbon fiber, and can optionallybe coated with a material, such as, for example, titanium, to make rod50 more compatible with MRI use. It is contemplated that the rod 50 maybe formed of any suitable material having suitable properties for thisapplication. Rod 50 has a first diameter. The length of rod 50 can bevaried depending on the need for a particular application.

Pin 60 can include a bone-engaging end, such as a self-tapping end 62,that is inserted into bone 70, 72. The pin 60 may also be constructedfrom any suitable biocompatible material. Optionally, end 62 can becoated with an antimicrobial material, such as, for example, silver orsilver ions, in order to reduce the likelihood of infection. Pin 60 hasa second diameter, smaller than the first diameter of rod 50. The lengthand diameter of pin 60 can vary, depending on the patient or the injury,as well as surgeon preference.

While FIGS. 1A and 2 show fixator assembly 100 being used to secure asingle rod 50 and a single pin 60, those skilled in the art willrecognize that fixator assembly 100 can, depending upon the particularsituation and injury, be used to connect two rods 50, as shown in FIG.1, or even two pins 60 (not shown).

As shown in FIG. 4, fixator assembly 100 includes a longitudinal axis102 extending therethrough. As used herein, the terms “longitudinal”,“longitudinally”, “axial”, and “axially” refer to directions along thelength of longitudinal axis 102 or to directions extending parallel tolongitudinal axis 102. Further, the terms “radial” and “radially” referto directions extending perpendicular to or extending outwardly fromlongitudinal axis 102.

Referring now to FIGS. 2 and 3, fixator assembly 100 includes a shaft110 and a plurality of clamp assemblies 120, 150 extending along shaft110. Shaft 110 extends along longitudinal axis 102. A biasing member 160is disposed between adjacent of the plurality of clamp assemblies 120,150. A cap, or ratchet, assembly 170 secures clamp assemblies 120, 150onto shaft 110.

Shaft 110 has a distal end 112 and a proximal end 114 extending awayfrom distal and 112. As used herein with respect to fixator assembly100, the term “distal” refers to a direction toward the bottom of thepage of FIG. 4, and the term “proximal” refers to a direction toward thetop of the page of FIG. 4.

Distal end 112 includes a radially extending flange 116 and at least oneflat surface 117 extending proximally of flange 116. While FIG. 4 showstwo flat surfaces 117, those skilled in the art will recognize thatshaft 110 can include more or less than two flat surfaces 117.

Proximal end 114 of shaft 110 has at least one external thread 118.Optionally, a length of shaft 115 between distal end 112 and proximalend 114 can be generally circular, that is, devoid of any flat surfacesor threads. Shaft 110 is sufficiently long to allow for the insertion ofclamp assemblies 120, 150 and ratchet assembly 170 thereon.

Clamp assemblies 120, 150 extend along shaft 110 from distal end 112toward proximal end 114 such that clamp assembly 120 engages flange 116and clamp assembly 150 engages clamp assembly 120. While two clampassemblies 120, 150 are shown, those skilled in the art will recognizethat more than two clamp assemblies 120, 150 can be used with fixatorassembly 100. Alternatively, it can be envisioned that only a singleclamp assembly 120 is used with fixator assembly 100.

Clamp assemblies 120, 150 may be, although not necessarily, identical toeach other. Clamp assembly 120 includes a lower member 122 and an uppermember 124 extending proximally of lower member 122. Lower member 122includes an axially extending passage 126 that is sized to allow shaft110 to extend therethrough. Passage 126 can include internal flatsurfaces 128 that are adapted to engage with flat surfaces 117 on shaft110 to prevent lower member 122 of clamp assembly 120 from rotating withrespect to shaft 110.

Lower member 122 includes a first generally U-shaped portion 130 havinga radius that is sized to receive a portion of rod 50. Lower member 122also includes a second generally U-shaped portion 131, radially disposedaway from first concave portion 130, having a radius that is sized toreceive a portion of pin 60. As shown in FIG. 3, lower member 122 alsoincludes a plurality of tangs 132 extending outwardly therefrom in aproximal direction toward upper member 124.

Upper member 124 includes an axially extending passage 134 that is sizedto allow shaft 110 to extend therethrough. Upper member 136 furtherincludes a first generally inverted U-shaped portion 136 having a radiusthat is sized to receive a portion of rod 50, such that, when uppermember 124 is biased toward lower member 122, rod 50 is received in acavity 138 formed by first generally U-shaped portion 130 of lowermember 122 and first generally inverted U-shaped portion 136 of uppermember 124.

Upper member 124 also includes a second generally inverted U-shapedportion 140, radially disposed away from first generally invertedU-shaped portion 136, having a radius that is sized to receive a portionof pin 60, such that, when upper member 124 is biased toward lowermember 122, pin 60 is received in a cavity 142 formed by secondgenerally inverted U-shaped portion 131 of lower member 122 and secondgenerally inverted U-shaped 140 of upper member 124.

As shown in FIG. 3, upper member 124 also includes a plurality of slots144 formed therein, such that each slot 144 is adapted to releasablyreceive a tang 132 from lower member 122, thereby preventing uppermember 124 from rotating about longitudinal axis 102 relative to lowermember 122. Upper member 124 also includes a spring cavity 146 that issized to receive biasing member 160. A toothed locking half 148surrounds spring cavity 146.

Clamp assembly 150 is similar to clamp assembly 120 with the exceptionthat, instead of internal flat surfaces 128, clamp assembly 150 includesa member 122′ having an axially extending passage 126′ sufficientlylarger than the diameter of shaft 110 such that clamp assembly 150 isfreely rotatable about shaft 110 and is also rotatable relative to clampassembly 120. As shown in FIGS. 3 and 4, clamp assembly 150 is insertedover shaft 110 “upside down” relative to clamp 120 such that toothedlocking half 148 of clamp assembly 150 is engageable with toothedlocking half 148 of clamp assembly 120 such that, when clamp assembly150 is biased against clamp assembly 120, toothed locking half 148 ofclamp assembly 150 engages toothed locking half 148 of clamp assembly120, preventing rotation of clamp assembly 150 with respect to clampassembly 120.

Each toothed locking half 148 includes a plurality of teeth or the like.In an exemplary embodiment, each toothed locking half 148 includes about90 teeth, such that clamp assembly 150 can be indexed with respect toclamp assembly 120 about 4°. Those skilled in the art, however, willrecognize that each toothed locking half 148 can include more or lessthan 90 teeth, such that the amount indexing of clamp assembly 150 withrespect clamp assembly 120 is adjustable accordingly.

As shown in FIG. 3, biasing member 160 is disposed between clampassembly 120 and clamp assembly 150 and is retained between clampassembly 120 and clamp assembly 150 within spring cavities 146. In anexemplary embodiment, biasing member 160 is a helical spring, althoughthose skilled in the art will recognize that other types of biasingmembers can be used. Biasing member 160 biases clamp assembly 120 andclamp assembly 150 apart from each other, such that clamp assembly 120and clamp assembly 150 securely engage rod 50 that may be inserted intocavity 138 and/or pin 160 that may be inserted into cavity 142.

Referring to FIGS. 3-5, ratchet assembly 170 is disposed over proximalend 114 of shaft 110, such that ratchet assembly 170 biases clampassemblies 120, 150 toward distal end 112 of shaft 110 and flange 116 sothat clamp assemblies 120, 150 are not rotatable with respect to eachother. A washer 162 is axially disposed between second clamp assembly150 and ratchet assembly 170 to distribute compressive forces applied byratchet assembly 170 onto clamp assembly 150.

Ratchet assembly 170 comprises includes a ratcheting buttress 172 thatis adapted to translate axially along shaft 110 from proximal end 114toward distal end 112. Ratcheting buttress 172 comprises a radiallyextending annular flange 174 having an axially extending hole 176therein. Hole 176 is sized to allow shaft 112 to extend therethrough. Atang 177 extends longitudinally outwardly from flange 174.

A plurality of fingers 178 extend proximally around hole 176. Each ofthe plurality of fingers 178 has a plurality of longitudinally spacedinternal ratchet teeth 180 adapted to engage external thread 118 onproximal end 114 of shaft 110. A gap 181 extends between each ofadjacent fingers 178 to allow fingers 178 to bias away from longitudinalaxis 102, thereby allowing thread 118 to ratchet along ratchet teeth 180when ratchet assembly 170 is pressed onto shaft 110.

A ratchet housing 182 is disposed over ratcheting buttress 172. Ratchethousing 182 includes a distal end 184 having a radially extendinghousing flange 186 that is adapted to engage buttress flange 174. Flange186 includes a slot 188 that is adapted to receive tang 177 from flange174 such that, when tang 177 is inserted into slot 188, ratchet housing182 is not rotatable relative to ratcheting buttress 172.

An exterior surface of housing flange 186 includes a contoured surface,such as, for example, a knurled surface, that provides a grippingsurface for the user to be able to manually rotate ratchet housing 182about shaft 110. An interior of housing flange 186 includes a firstradially extending cavity 190 adapted to receive annular flange 174 ofratchet buttress 172.

Ratchet housing 182 further includes a proximal body 192 having aninternally threaded passage 193 with at least one internal thread 194adapted to threadably engage external thread 118 on shaft 110. Body 192further comprises a plurality of flat surfaces 196 extending around aperimeter thereof. Flat surfaces 196 allow for the application of atool, such as, for example, a wrench or other torquing device (notshown) to tighten fixator assembly 100 in order to secure rod(s) 50and/or pin(s) 60. Body 192 also includes a second radially extendingcavity 198 that is adapted to receive the plurality of fingers 178. Asshown in FIG. 4, cavity 198 is sufficiently large to allow fingers 178to bias away from shaft 110 to allow ratcheting buttress 172 to be sliddistally along shaft 110.

To assemble fixator assembly 100, first clamp assembly 120 is slid fromproximal end 114 of shaft 110 to distal end 112 shaft 110, bottoming outon flange 116. First clamp assembly 120 is aligned such that toothedlocking half 148 is facing proximal end 114 of shaft 100. Next, biasingmember 160 is slid along shaft 110 such that at least a portion ofbiasing member 160 is seated within spring cavity 146.

Second clamp assembly 150 is then slid from proximal end 114 of shaft110, toward first clamp assembly 120. Second clamp assembly 150 isaligned such that toothed locking half 148 is facing distal end 112 ofshaft 100 so that at least a remaining portion of biasing member 160 isseated within spring cavity 146 in second clamp assembly 150 and so thattoothed locking half 148 of second clamp assembly 150 is facing toothedlocking half 148 of first clamp assembly 120.

Washer 162 is slid over shaft 110. Ratchet assembly 170 is then slidover shaft 110 so that internal thread 194 engages external threads 118on shaft 110. At this point, cavities 138, 142 are sufficiently large toallow rod 50 be slid into cavity 138 and pin 60 to be slid into cavity142 and also to allow second clamp assembly 150 to axially rotaterelative to first clamp assembly 120.

In this condition, the surgeon can align rod 50 and pin 60 in desiredpositions with respect to fixator assembly 100. The surgeon can thenprovisionally tighten ratchet assembly 170 by further sliding ratchetassembly 170 distally along shaft 110 and then perform a finaltightening of fixator assembly 100 by applying a wrench or other courtapplying device (not shown) to flat surfaces 196 on ratchet housing 182and rotating ratchet housing 182 relative to shaft 110.

Ratchet assembly 170 allows for the rapid application of clampassemblies 120, 150 onto bar 50 and/or pin 60. Ratchet assembly 170 alsoprovides a quick method for provisional tightening of fixator assembly100 while the surgeon is assembling fixator assembly 100 with bar(s) 50and pin(s) 60. Once set, a final tightening of ratchet assembly 170 canbe applied using a torque limiting adapter, for example, under power.

According to one embodiment, a method of installing the external fixatorsystem, for example, at the site of one or more broken bones, mayinclude inserting one or more pins 60 into the afflicted bone (forexample, on opposite sides of the fracture); attaching one or morefixator assemblies 100 to each pin 60; and securing the one or more pins60 to adjacent pins 60 by connecting one or more rods 50 betweenadjacent fixator assemblies 100. If the construct needs to be extended,for example, to bridge multiple bones or multiple fractures, the samefixator assembly 100 can also be used to connect two or more rods 50together.

An alternative embodiment of an external fixator assembly 200 (“fixatorassembly 200”) is shown in FIGS. 6-10. FIG. 6 shows fixator assembly 200being used with both rods 50 and pins 60 to secure and stabilizeadjacent bones 70, 72 in a patient. FIG. 7 shows fixator assembly 200being used to secure two rods 50 in a generally parallel arrangement,while FIG. 7A shows fixator assembly 200 being used to secure a singlerod 50 and a single pin 60 in a skewed arrangement.

Referring to the exploded view of fixator assembly 200, shown in FIG. 8and the sectional view shown in FIG. 9, fixator assembly 200 includes afirst shaft 202 having a first coupling end 204 and a first free end206. First coupling end 204 has an outer diameter D1. First free end 206has a narrower diameter than outer diameter D1. First coupling end 204terminates in a first lip 207, having a generally flat face 208 and agenerally convex outer face 209. A first longitudinal axis 210 extendsalong the length of first shaft 202.

Similarly, a second shaft 212 has a second coupling end 214 and a secondfree end 216. Second coupling end 214 has an outer diameter D2. Secondfree end 216 has a narrower diameter than outer diameter D2. Secondcoupling end 214 terminates in a second lip 217, having a generally flatface 218 and a generally convex outer face 219. A second longitudinalaxis 220 extends along the length of second shaft 212.

A coupling 230 pivotally retains first coupling end 204 and secondcoupling end 214 therein. Coupling 230 includes a first cup, orclamshell portion 232 having a concave interface 234 that is contouredto receive generally convex outer face 209 of first coupling end 204.Additionally, first clamshell portion 232 includes an opening 236,having a diameter D3, such that outer diameter D1 of first coupling end204 is smaller than the diameter D3, but first lip 207 is larger thanthe size of opening 236 such that, when first shaft 202 is insertedthrough opening 236, first lip 207 is retained within first clamshellportion 232.

Likewise, coupling 230 also includes a second cup, or clamshell portion242 having a concave interface 244 that is contoured to receivegenerally convex outer face 219 of second coupling end 214.Additionally, second clamshell portion 242 includes an opening 246,having a diameter D4, such that outer diameter D2 of second coupling end214 is smaller than the diameter D4, but second lip 217 is larger thanthe size of opening 246 such that, when second shaft 212 is insertedthrough opening 246, second lip 217 is retained within second clamshellportion 242.

In an exemplary embodiment, first clamshell portion 232 includes femalethreads 238 and second clamshell portion 242 includes matching malethreads 248 such that first clamshell portion 232 can be threadedlyconnected to second clamshell portion 242. Optionally, to prevent firstclamshell portion 232 from being separated from second clamshell portion242, first clamshell portion 232 can be welded or otherwise permanentlysecured to second clamshell portion 242 at the connection of femalethreads 238 and male threads 248.

As used herein, the term “inner” is used to define a direction towardcoupling 230, and the term “outer” is used to define a direction awayfrom coupling 230. A first clamp assembly 250 is disposed on first shaft202 between coupling 230 and first free end 206 of first shaft 202.First clamp assembly 250 includes a first inner clamp member 252disposed proximate to coupling 230. First inner clamp member 252 has afirst inner slot 260. First inner slot 260 has an open end 262, locatedat a shaft end 263, and a blind end 264, located at a finger end 265.Finger end 265 includes an arcuate cutout 266 that extends in an arcgreater than 90°. A drill passage 268 extends obliquely through fingerend 265 to allow for the formation of blind end 264.

First inner clamp member 252 also includes a concave surface 269 thatengages concave interface 234 of first clamshell portion 232 so thatfirst inner clamp member 252 is slidable along at least a portion ofconcave interface 234. Additionally, first inner clamp member 252includes a through-opening 270 sized to allow first shaft 202 to passtherethrough. Through-opening 270 is sized such that a minimum clearanceexists between through-opening 270 and first shaft 202.

First clamp assembly 250 further includes a first outer clamp member 272disposed proximate to first free end 206. First outer clamp member 272has a first outer slot 280. First outer slot 280 has an open end 282,located at shaft end 283, and a blind end 284, located at a finger end285. Finger end 285 includes an arcuate cutout 286 that extends in anarc greater than 90°. A drill passage 288 extends obliquely throughfinger end 285 to allow for the formation of blind end 284. Similar toconcave surface 269 in first inner clamp member 252, first outer clampmember 272 also includes a concave surface 289. Additionally, firstouter clamp member 272 includes a through-opening 290 sized to allowfree end 206 of first shaft 202 to pass therethrough.

In an exemplary embodiment, first outer clamp member 272 is generally amirror image of first inner clamp member 252 across a transverse axis291. When first inner clamp member 252 and first outer clamp member 272are assembled on shaft 202, as shown in FIG. 9, a retaining cavity 292is formed between finger end 265 and finger end 285. Retaining cavity292 has a wall portion that extends an arc of greater than 180°. In anexemplary embodiment, retaining cavity 292 is sized to allow theinsertion of rod 50 therein.

A first biasing member 294 is disposed in first inner slot 260 and firstouter slot 280. In an exemplary embodiment, first biasing member 294 isa C-shaped spring having a first end 296 that is inserted into blind end264 of first inner slot 260 and a second end 297 that is inserted intoblind end 284 of first outer slot 280 such that first biasing member 294biases first inner clamp member 252 toward first outer clamp member 272.

A first washer 295 is disposed over first shaft 202 and against firstouter clamp member 272. First washer 295 has a contoured inner surface297 for engagement with concave surface 289. A nut 298 is threaded ontofirst shaft 202 to secure first clamp assembly 250 against coupling 230.

Similar to first clamp assembly 250, a second clamp assembly 350 isdisposed on second shaft 212 between coupling 230 and second free end216. Second clamp assembly 350 includes a second inner clamp member 352disposed proximate to coupling 230. Second inner clamp member 352 has asecond inner slot 360. Second inner slot 360 has an open end 362,located at a shaft end 363 and a blind end 364, located at a finger end365. Finger end 365 includes an arcuate cutout 366 that extends in anarc greater than 90°. A drill passage 368 extends obliquely throughfinger end 365 to allow for the formation of blind end 364.

Second inner clamp member 352 also includes a concave surface 369 thatengages concave interface 334 of second clamshell portion 242 so thatsecond inner clamp member 352 is slidable along at least a portion ofconcave interface 334. Additionally, second inner clamp member 352includes a through-opening 370 sized to allow second shaft 212 to passtherethrough. Through-opening 370 is sized such that a minimum clearanceexists between through-opening 370 and second shaft 212.

Second clamp assembly 350 further includes a second outer clamp member372 disposed proximate to second free end 216. Second outer clamp member372 has a second outer slot 380. Second outer slot 380 has an open end382, located at shaft end 383 and a blind end 384, located at a fingerend 385. Finger end 385 includes an arcuate cutout 386 that extends inan arc greater than 90°. A drill passage 388 extends obliquely throughfinger end 385 to allow for the formation of blind end 384. Similar toconcave surface 369 in second inner clamp member 352, second outer clampmember 372 also includes a concave surface 389. Additionally, secondouter clamp member 372 includes a through-opening 390 sized to allowfree end 216 of second shaft 212 to pass therethrough.

In an exemplary embodiment, second outer clamp member 372 is generally amirror image of second inner clamp member 352 across a transverse axis391. When second inner clamp member 352 and second outer clamp member372 are assembled on shaft 212, as shown in FIG. 9, a retaining cavity392 is formed between finger end 365 and finger end 385. Retainingcavity 392 has a wall portion that extends an arc of greater than 180°.In an exemplary embodiment, retaining cavity 392 is sized to allow theinsertion of pin 60 therein.

A second biasing member 394 is disposed in second inner slot 360 andsecond outer slot 380. In an exemplary embodiment, second biasing member394 is a C-shaped spring having a first end 396 that is inserted intoblind end 364 of second inner slot 360 and a second end 397 that isinserted into blind end 384 of second outer slot 380 such that secondbiasing member 394 biases second inner clamp member 352 toward secondouter clamp member 372.

A second washer 395 is disposed over second shaft 212 and against secondouter clamp member 372. Second washer 395 has a contoured inner surface397 for engagement with concave surface 389. A nut 398 is threaded ontosecond shaft 212 to secure second clamp assembly 350 against coupling230.

To assemble fixator assembly 200, first shaft 202 is inserted into firstclamshell portion 232, such that first lip 207 is seated in firstclamshell portion 232 and second shaft 212 and second shaft 212 isinserted into second clamshell portion 242, such that second lip 217 isseated in second clamshell portion 242. First and second clamshellportion 232, 242 are then fixedly secured to each other.

First inner clamp member 252 and first outer clamp 272 are placed nextto each other, such that first inner slot 260 and first outer slot 280are aligned with each other, forming first clamp assembly 250. Firstbiasing member 294 is then inserted through first inner slot 260 andfirst outer slot 280 such that first end 296 of first biasing member 294is inserted into blind end 264 of first inner slot 260 and second end297 of biasing member 294 is inserted into blind end 284 of first outerslot 280, thereby securing first inner clamp member 252 and first outerclamp member 272 to each other and providing a compressive force to biasfinger end 265 of first inner clamp member 252 and finger end 285 offirst outer clamp member 272 toward each other.

First clamp assembly 250 is then slid over first shaft 202 such thatfirst shaft 202 extends through through-openings 270, 290 and firstshaft 202 extends through first inner slot 260 and first outer slot 280such that first shaft 202 retains first biasing member 294 in firstinner slot 260 and first outer slot 280. Washer 295 is slid over firstshaft 202 and nut 298 is then threaded onto first shaft 202 to securefirst clamp assembly 250 against coupling 230.

Similarly, second inner clamp member 352 and second outer clamp 372 areplaced next to each other, such that second inner slot 360 and secondouter slot 380 are aligned with each other, forming second clampassembly 350. Second biasing member 394 is then inserted through secondinner slot 360 and second outer slot 380 such that first end 396 ofsecond biasing member 394 is inserted into blind end 364 of second innerslot 360 and second end 397 of biasing member 394 is inserted into blindend 384 of second outer slot 380, thereby securing second inner clampmember 352 and second outer clamp member 372 to each other and providinga compressive force to bias finger end 365 of second inner clamp member352 and finger end 385 of second outer clamp member 372 toward eachother.

Second clamp assembly 350 is then slid over second shaft 212 such thatsecond shaft 212 extends through through-openings 370, 390 and secondshaft 212 extends through second inner slot 360 and second outer slot280 such that second shaft 212 retains second biasing member 394 insecond inner slot 360 and second outer slot 380. Washer 395 is slid oversecond shaft 212, and nut 398 is then threaded onto second shaft 212 tosecure second clamp assembly 350 against coupling 230.

Rod 50 can be inserted into retaining cavity 292. Because retainingcavity 292 has a wall portion that defines an arc of greater than 180°,with rod 50 in retaining cavity 292, the compressive action of biasingmember 294 and the tightening of nut 298 securely retain rod 50 withinretaining cavity 292.

Similarly, pin 60 can be inserted into retaining cavity 392. Becauseretaining cavity 392 has a wall portion that defines an arc of greaterthan 180°, with pin 60 in retaining cavity 392, the compressive actionof biasing member 394 and the tightening of nut 298 securely retain pin60 within retaining cavity 392.

In order to rotate first clamp assembly 250 about first shaft 210, nut298 can be loosened sufficiently to allow such rotation. The compressiveaction of first biasing member 294 retains rod 50 within retainingcavity 292 to allow such rotation, without adversely affecting theretention of rod 50 within first clamp assembly 250.

Likewise, in order to rotate second clamp assembly 350 about secondshaft 220, nut 398 can be loosened sufficiently to allow such rotation.The compressive action of second biasing member 394 retains pin 60within retaining cavity 392 to allow such rotation, without adverselyaffecting the retention of pin 60 within second clamp assembly 350.

Additionally, because diameter D1 of first coupling end 204 is smallerthan diameter D3 of opening 236 in first clamshell portion 232 anddiameter D2 of second coupling end 214 is smaller than diameter D4 ofopening 246 in second clamshell portion 242, first longitudinal axis 210of first shaft 202 does not necessarily have to be collinear with secondlongitudinal axis 220 of second shaft 212. As shown in FIG. 10, firstlongitudinal axis 210 can extend at an oblique angle β relative tosecond longitudinal axis 220, allowing for first clamp assembly 250 toangularly pivot relative to second clamp assembly 350, thereby allowingfor angular adjustment of first clamp assembly 250 relative to secondclamp assembly 350. FIG. 7A shows an example of such angular adjustment.

According to one embodiment, a method of installing the external fixatorsystem, for example, at the site of one or more broken bones, mayinclude inserting a first pin 60 into the afflicted bone on one side ofthe fracture; inserting a second pin 60 on an opposite side of thefracture; attaching a first fixator assembly 200 to the first pin 60 anda second fixator assembly 200 to the second pin 60; articulating thefirst or second clamp assembly 250, 350 relative to the other of thefirst or second clamp assembly 250, 350 into a position for receivingthe rod 50; connecting the rod 50 between the first and second fixatorassemblies 200 in order to secure the first and second pins 60 together.If the construct needs to be extended, for example, to bridge multiplebones or multiple fractures, a third fixator assembly 200 may bearticulated and positioned to secure and connect the rod 50 to anadditional rod 50.

It will be further understood that various changes in the details,materials, and arrangements of the parts which have been described andillustrated in order to explain the nature of this invention may be madeby those skilled in the art without departing from the scope of theinvention as expressed in the following claims.

What is claimed is:
 1. A system for fixating a fractured bone, saidsystem comprising: a first rod; a first pin; and a first externalfixator assembly comprising: a first shaft having a distal end and aproximal end, the proximal end having at least one external thread; afirst rod clamp assembly configured to attach to the first rod; a firstpin clamp assembly configured to attach to the first pin; a firstbiasing member disposed between the first rod clamp assembly and thefirst pin clamp assembly; and a first cap assembly disposed over theproximal end of the shaft to secure the first rod clamp assembly and thefirst pin clamp assembly to the shaft, wherein the first cap assemblycomprises a ratcheting buttress adapted to translate along the shaftfrom the proximal end toward the distal end.
 2. The system of claim 1,wherein the distal end of the shaft comprises a flange.
 3. The system ofclaim 2, wherein the distal end of the shaft, proximal of the flange,further comprises at least one flat surface.
 4. The system of claim 3,wherein at least one of the first rod clamp assembly and the first pinclamp assembly comprises an internal surface adapted to engage the atleast one flat surface of the shaft, preventing rotation of the at leastone of the first rod clamp assembly and the first pin clamp assemblywith respect to the shaft.
 5. The system of claim 1, wherein at leastone of the first rod clamp assembly and the first pin clamp assemblycomprises an upper member and a lower member.
 6. The system of claim 5,wherein one of the upper member and the lower member comprises a tangextending outwardly therefrom toward the other of the upper member andthe lower member, and wherein the other of the upper member and thelower member comprises a slot adapted to releasably receive the tang. 7.The system of claim 1, further comprising a second external fixatorassembly comprising: a second shaft having a distal end and a proximalend, the proximal end having at least one external thread; a second rodclamp assembly configured to attach to the first rod; a second pin clampassembly configured to attach to a second pin; a second biasing memberdisposed between the second rod clamp assembly and the second pin clampassembly; and a second cap assembly disposed over the proximal end ofthe second shaft to secure the second rod clamp assembly and the secondpin clamp assembly to the second shaft.
 8. The system of claim 1,wherein at least one of the first rod clamp assembly and the first pinclamp assembly is rotatable about the shaft prior to being secured. 9.The system of claim 1, wherein the ratcheting buttress comprises aradial flange having a hole therein, the hole being sized to allow theshaft to extend therethrough, and a plurality of fingers extendingproximally around the hole, each of the plurality fingers having aplurality of internal ratchet teeth adapted to engage the at least oneexternal thread on the proximal end of the shaft.
 10. The system ofclaim 9, further comprising a ratchet housing disposed over theratcheting buttress.
 11. The system of claim 10, wherein at least one ofthe ratcheting buttress and the ratchet housing comprises a tangextending outwardly therefrom and wherein the other of the ratchetingbuttress and the ratchet housing comprises a slot adapted to receive thetang such that, when the tang is inserted into the slot, the ratchethousing is not rotatable relative to the ratcheting buttress.
 12. Thesystem of claim 11, wherein the ratchet housing comprises at least oneinternal thread, the at least one internal thread being threadablyengageable with the at least one external thread on the proximal end ofshaft.
 13. A system for fixating a fractured bone, said systemcomprising: a rod; a plurality of pins; and a plurality of externalfixator assemblies, each comprising: a shaft having a distal end and aproximal end, the proximal end having an external thread; a rod clampassembly configured to attach to the rod; a pin clamp assemblyconfigured to attach to one of the plurality of pins; a biasing memberdisposed between the rod clamp assembly and the pin clamp assembly; anda cap assembly configured to threadedly engage the external thread tosecure the first rod clamp assembly and the first pin clamp assembly tothe shaft, wherein the cap assembly comprises a ratcheting buttressadapted to translate along the shaft from the proximal end toward thedistal end.
 14. The system of claim 13, wherein the distal end of eachshaft comprises a flange.
 15. The system of claim 14, wherein the distalend of each shaft, proximal of each flange, further comprises at leastone flat surface.
 16. The system of claim 15, wherein each rod clampassembly and each pin clamp assembly comprise an internal surfaceadapted to engage the one of the at least one flat surface, preventingrotation each rod clamp assembly and each pin clamp assembly withrespect to the shaft.
 17. The system of claim 13, wherein each rod clampassembly and each pin clamp assembly comprise an upper member and alower member.
 18. The system of claim 17, wherein one of the uppermember and the lower member comprises a tang extending outwardlytherefrom toward the other of the upper member and the lower member, andwherein the other of the upper member and the lower member comprises aslot adapted to releasably receive the tang.
 19. The system of claim 13,wherein each rod clamp assembly and each pin clamp assembly arerotatable about an associated shaft prior to being secured.